1. Field of the Invention
The present invention relates to a dual-function rotary machine and, more particularly, to a combined rotary pump and compressor unit capable of simultaneously pumping a liquid and a gaseous fluid. Such a combined pump and compressor unit may be suitably mounted on a vehicle engine for serving and operating both a power-steering system and an air-conditioning system of the vehicle by a single unit.
2. Description of the Prior Art
In vehicles equipped with both power-steering systems and air-conditioning systems, it has been customary to install an oil pump for feeding a working fluid under pressure to the power steering system separately from a compressor for pressurizing a refrigerant for the air-conditioning system. The pump and the compressor are mounted on the engine by brackets or supports independently from one another and are driven independently by the engine through their own drive belts and pulleys. The reasons for such independent installation and independent drive stem from the fact that the oil pump must be driven continuously as long as the engine is running, to maintain the power steering system in a state wherein it is operable at any time it is desired. Conversely, demand for the compressor output varies in accordance with the temperature of the vehicle room, i.e., operation of the compressor is not required during an "off" cycle of the air-conditioning system. Thus, in the prior art, the refrigerant compressor is not only mounted on the engine independently from the oil pump but is also generally provided with an electromagnetic clutch adapted to disconnect the compressor shaft from the drive pulley when the refrigerant output is not necessary.